Oil return device for flooded evaporators



y 1934. T. c. FEDDERS ET AL 1,965,544

OIL RETURN DEVICE FOR FLOODED EVAPORATORS Filed Oct. 19, 1932 3nnentorb T/aeooore C 2089/6 Fran/M21 C 61798/ I ttorneg Patented July 3, 1934- UNITED STATES PATENT OFFICE on. RETURN DEVICE FOR FLOODED EVAPORATORS Theodore C. Fedders' and Fr' an'kliii G. Slagel,

Buffalo, N. Y., assig'nors to Fedders Manufac 4 Claims.

This invention relates to refrigerating apparatus, and it has particular reference to the pro-' vision of oil return means in a refrigeration evaporator of the flooded type.

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The invention provides for the interposition of a multistage oil rectifying device between an oil-bearing liquid body in the evaporator and the suction conduit thereof, wherein the oil, including incidental volumes of liquid refrigerant, is directed through a plurality of receivers before admission into the suction line. The device is provided with means for preferentially conveying oil from step to step and for permitting a rapid evaporation of the trapped liquid refrigerant in each step. During this process, certain portions of the device'are placed in the path of the relatively warm gases en route to the suction line, whereby a more rapid separation of the liquid refrigerant from the oil is obtainable.

A practical embodiment of the invention set forth in the specification and the drawing illustrates the application of this principle to a well known form of evaporator construction. In the drawing,

Fig. 1 is a longitudinal section through a refrigerator header showing the application of the rectifying device to the oil return means thereof;

Fig. 2 is a cross section on the line 2-2 of Fig. 1.

The invention has been found applicable in an evaporator for a flooded system of refrigeration including an open type of float. The operation in this evaporator is briefly as follows: Liquid refrigerant enters a header 10 through a valve 12 which is controlled by an open pivoted float 13 in response to the liquid level in the header. The refrigerant, in expanding and absorbing heat units through the walls of the evaporator, evaporates and is drawn out of the header through a suction conduit 14. The lubricant, normally in solution with the refrigerant, does not evaporate during this action, and it forms a layer at the surface of the liquid refrigerant, where it is continuously subjected to the ebullient action of the underlying refrigerant. Normally, this action results in the delivery of an oil and gas mist into the conduit 14 which is a desirable condition. During a more violent or eruptive action of the refrigerant, however, small quantities of liquid refrigerant are projected into the float and are directed, with the deposited oil volumes, into the conduit 14 with undesirable results, such as backfrosting or injury to the compressor.

The present invention is therefore directed to means for rectifying the oil deposited in the first receiver or float 13 before admission into the Cori duit 14. Such means comprise a second receiver or open cup 16 secured to the depending end 17 of the suction conduit 14. A plurality of liquidtransfer means or wicks 18 formed of folded fine mesh screen are mounted on the cup 16 and each is formed with a long end 19 depending in spaced relation to the bottom of the float 13, and a shortend 21 extending within the cup 16 and terminating above the end of the conduit 14. A protective cover 22 is secured to the conduit 14 and it closely overlies the open end of the cup 16.

The operation of the device is substantially uni-- form, either during normal or more severe evaporating action in the header, since it will be ap- 7 parent that oil deposited in the float 13 will eventually reach the siphoning level of the wick ends 19 and be conveyed thereby into the cup 16 for withdrawal through the conduit 14. Prior to attaining the siphoning level in the float 13, as indicated by the numeral 20, the oil retains the longer wick end 19 in moist condition preparatory to its siphoning function. The wick ends 21 are retained above the level of the suction conduit end 17 so that liquid will not be re-siphoned go: from the cup 16 to the float 13 in the event of a lowering of the liquid level in the float through evaporation of liquid refrigerant therein. This delayed yet continuous oil return action is devised to separate the oil from adventitious vol- 51* umes of liquid refrigerant entering the float 13, as it will be apparent that a gravitational separating action will occur in the float 13 with the re sult that the oil will be withdrawn by the wicks 18, and, concurrently, the liquid refrigerant '0 therein will be continuously subj ected to evaporation. Even with this arrangement, small quantitles of liquid refrigerant may be drawn up by the wicks and deposited in the cup 16. In this event, a second separating action occurs in the 9 cup, and oil is thus preferentially drawn into the conduit 14 while the underlying small body of liquid refrigerant is subjected to evaporation by its proximity to the relatively warm gases flowing into the conduit 14.

It is to be noted that the provision of a plurality of slow-action wicks is to be preferred to a single faster wick, since the slower wicks present a large evaporative surface to the relatively warm gases flowing through the space between the 1 cover 22 and the cup 16, with a resulting evaporation of liquid refrigerant carried by the wicks.

The cup 16 is suitably located relative to the bottom of the float 13, so that the float remains buoyant in the event the liquid level therein 1 too sarily' limited in its use to an open float as de-' scribed, as it may be installed as a separate and stationary unit in a header having a closed float with satisfactory results. The invention is to be construed, therefore, in view of the following claims.

We claim:

1. In a refrigerating apparatus comprising an evaporator having an inlet conduit for admitting refrigerant and oil admixed therewith, a control valve for said inlet, an open float in the evaporator for controlling the valve, said float being adapted to receive by ebullition quantities of oil admixed with small volumes of liquid refrigerant, a suction conduit extending into said float, a cup secured to the end of the conduit and receiving the end of the conduit within its cavity, said cup being spaced from the bottom of the float, and wick means extending from the interior of the cup to a point adjacent the bottom of the float.

2. In a refrigerating apparatuscomprising an evaporator having an inlet conduit for admitting refrigerant and oil admixed therewith, a control valve. for said inlet, an open float in the evaporator for controlling the valve, said float being adapted to receive by ebullition quantities of oil admixed with small volumes of liquid refrigerant, a suction conduit extending into said float, a cup secured to the end of the conduit and receiving the end of the conduit within its cavity, said cup being spaced from the bottom of the float, and wick means extending from the interior of the cup to a point adjacent the bottom of the float, said cup being positioned in said float at a point below the buoyancy level thereof.

3. In a refrigerating apparatus comprising an evaporator having means for admitting refrigerant and oil admixed therewith, receiver means in the evaporator for receiving the products of ebullition therefrom for gravitational separation into oil and liquid refrigerant bodies, a second receiver in the" evaporator, wick means extending fr'om the 011 surface; in the first receiver to the interior of the second receiver, an outlet conduit entering the second receiver in spaced relation from the bottom thereof, said conduit being adapted to withdraw gas volumes from the evaporator and oil volumes from the second receiver, and means for directing the gas volumes in their passage to the conduit over the wicks to obtain heat exchange therewith and resulting refrigerant evaporation therein.

4. In a refrigerating apparatus comprising an evaporator having means for admitting refrigerant and oil admixed therewith, receiver means comprising an open vessel mounted in the evaporator with its opening above the liquid level therein, said receiver being adapted to receive the products of ebullition for gravitational separation into oil and liquid bodies, an open cup disposed within the receiver adjacent the bottom thereof, liquid transfer means between the receiver and cup for withdrawing oil from the receiver, and an outlet conduit entering said cup to withdraw oil therefrom. THEODORE C. FEDDERS.

FRANKLIN G. SLAGEL. 

